Use of liquid and gel monopropellants for well stimulation

ABSTRACT

An apparatus and process for fracturing wells is provided. In one example, an apparatus includes an electric liquid monopropellant device including a volume of electric liquid monopropellant and a detonation cord in proximity to the electric liquid monopropellant device to ignite the volume of electric liquid monopropellant upon activation of the detonation cord. The detonation cord is adapted to ignite the electric liquid monopropellant at pressures exceeding 200 psi, and in some examples, exceeding 500 or 1,000 psi. The detonation cord can be wrapped around the electric liquid monopropellant device in a variety of configurations to increase combustion rates and/or shape the event pulse of the combustion.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Serial No. 62/447,294, titled “USE OF LIQUID AND GEL MONOPROPELLANTS FOR WELL STIMULATION,” filed Jan. 17, 2017. The contents of which are incorporated herein by reference for all purposes.

FIELD

This application relates generally to systems and processes for well stimulation, and in particular for stimulating subsurface hydrocarbon reservoirs by the introduction or injection of liquid and/or gel monopropellants.

RELATED ART

The oil industry has increasingly relied upon enhanced oil recovery methods, including well stimulation methods, for accessing and extracting oil. Stimulation methods typically include injecting a treatment fluid (e.g., water) down a well to create a hydraulic fracture in a subsurface structure. In some applications, in situ combustion is sometimes used. For instance, solid propellant charges have been used for many years to create sufficient pressure via the treatment fluid for fractures in oil, gas, and water formations surrounding wells.

It is desired to have increased control of propellant charges for creating adequate pressures for extending fractures into the surrounding formations. It is further desired to use less treatment fluid to create such factures.

SUMMARY

According to one aspect and example, an apparatus for fracturing wells is provided. In one example, an apparatus includes an electric liquid monopropellant device including a volume of electric liquid monopropellant, and a detonation cord in proximity to the electric liquid monopropellant device to ignite the volume of electric liquid monopropellant. The detonation cord is adapted to ignite the electric liquid monopropellant at pressures exceeding 200 psi, and in some examples, exceeding 500 or 1,000 psi. The detonation cord can be wrapped around the electric liquid monopropellant device in a variety of configurations to increase combustion rates and/or shape the event pulse of the combustion. Further, the liquid monopropellant devices are adapted to combust at temperatures less than 300 degrees Celsius.

In some examples, a plurality of electric liquid monopropellant devices can be disposed within a well tool, and the plurality of electric liquid monopropellant devices in proximity to the detonation cord. Further, at least one shaped charge device may be disposed within the well tool and in proximity to the detonation cord to combust upon activation of the detonation cord.

In some examples, electrically conductive wires are disposed in contact with the electric liquid monopropellant for sensitizing the electric liquid monopropellant prior to combustion.

In another aspect, an apparatus includes a container including an electric liquid monopropellant therein. The container may include a bag, tube, or other package for containing the electric liquid monopropellant. The apparatus can further include a detonation cord, an electrode, and/or an electric match to initiate combustion.

In another aspect, an exemplary process is provided for fracturing wells. In one example, a process includes introducing an electric liquid monopropellant into a well and igniting the electric liquid monopropellant in the well. In some examples, the liquid monopropellant is ignited when the pressure exceeds 200 psi, and in some examples when the pressure exceeds 500 or 1000 psi. The electric liquid monopropellant can be introduced via a well gun.

BRIEF DESCRIPTION OF THE FIGURES

The present application can be best understood by reference to the following description taken in conjunction with the accompanying figures, in which like parts may be referred to by like numerals.

FIGS. 1A-1E illustrate exemplary arrangements of electric liquid monopropellant devices, with or without the use of conventional shaped charges, within a well gun tool.

FIGS. 2A-2E illustrate various exemplary configurations of an electric liquid monopropellant devices and detonating cord.

FIGS. 3A-3C illustrate various exemplary configurations of an electric liquid monopropellant and detonating cord/wires.

FIGS. 4A-4C illustrate an exemplary process of pumping electrically ignitable monopropellant into a well casing and existing perforations and igniting to form new fractures.

FIG. 5 illustrates an exemplary electric liquid monopropellant device and detonation cord within a carrier gun.

FIG. 6 illustrates an exemplary electric liquid monopropellant device utilizing a partially insulated electrode for ignition.

DETAILED DESCRIPTION

The following description is presented to enable a person of ordinary skill in the art to make and use the various embodiments. Descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the present technology. Thus, the disclosed technology is not intended to be limited to the examples described herein and shown, but is to be accorded the scope consistent with the claims.

In one example of the present invention, an electric liquid monopropellant is used. The electric liquid monopropellant may be contained in a device or package (e.g., a container, bag, receptacle, etc.) and in close proximity to a detonation or ignition cord. For instance, a detonation cord can be at least partially wrapped around the electric liquid monopropellant device such that upon ignition of the detonation cord, the electric liquid monopropellant within the device or package detonates. In some examples, one or more electric liquid monopropellant devices can be disposed with one or more conventional shaped charge devices and proximate (e.g., wrapped) to a common detonation cord. In such examples, the shaped charge devices detonate at a faster rate than the electric liquid monopropellant, thereby providing a perforation of a well tool, well bore, and/or surrounding structure, prior to detonation of the electric liquid monopropellant.

In other examples, electric liquid monopropellant can be introduced or pumped into well structures directly, e.g., via a well or gun tool, without a device or package containing the liquid. This allows the electric liquid monopropellant to flow into cracks and other structures of the well. In some examples, the well bore can then be capped or otherwise pressurized and the electric liquid monopropellant detonated, thereby creating new fractures and/or extending existing fractures.

FIGS. 1A-1D illustrate various arrangements of shaped charges (SC) 102 and electric liquid monopropellant (ELP) devices 100 disposed within a well gun tool 110, which may be used introduce one or more ELP devices 100 into a well structure. In some examples, the ELP devices 100 can be packaged to operate in conjunction with or without SC 102 in perforation guns or gas generating guns (e.g., GasGun or StimTube) that use conventional solid propellants for well stimulation.

Additionally, FIG. 1E illustrates an arrangement of multiple ELP devices 100 without the use of shaped charges. In these examples, SC 102 and ELP devices 100 are shown disposed within a gun tool 110, which may used within a well casing, e.g., within a well formation or structure that is to be fractured.

Further, a detonation cord 112 is shown running adjacent to and/or through SC 102 and ELP devices 100. Upon ignition of detonation cord 112 the SC 102 and ELP devices 100 combust. Typically, SC 102 detonate more quickly than the ELP devices 100, perforating the casing of the well gun and/or structures within the well, which is followed by combustion of the ELP devices 100.

ELP devices 100 may include an electric liquid monopropellant, such as green electric monopropellant, e.g., a HAN based liquid monopropellant that can be electrically ignited. One such liquid monopropellant is sold under the product name “GEM Mod 3 Green Electrical Monopropellant,” and sold by Digital Solid State Propulsion Inc., which generally comprises Hydroxylammonium Nitrate/2,2′-dipyridyl/Ammonium Nitrate/Water/1,2,4-triazole/1H-pyrazole (see also, e.g., https://www.dsspropulsion.com/propellant-products/). Similar electric liquid monopropellants are described in U.S. Pat. No. 9,328,034, entitled “Liquid Electrically Initiated and Controlled Gas Generator Composition,” granted on May 3, 2016, the contents of which are incorporated herein by reference in its entirety. In some examples, the electric liquid monopropellant may also be in a gel form.

Such exemplary electric liquid monopropellants can further be gelled for use in such devices described herein. For example, gelling materials may include fumed silica, polyvinyl alcohol, and the like. Progressively thicker gels will cause the propellant to burn more slowly. Exemplary liquid propellants can also be foamed using such gelling agent described above and Nitrogen gas. For example, rapid mixing, high speed blending or other methods can be used to entrain and suspend small nitrogen bubbles in the propellant gel. The propellant can also be made to burn faster by adding silica micro-balloons. These bubbles or balloons will cause the propellant to burn faster in the tool because of the additional surface area created.

Such exemplary electric liquid monopropellants at normal surface temperatures and pressures typically require electrical power to ignite, however, at pressures typically found within wells, e.g., greater than 200 psi, and often greater than 500 or 1000 psi, the electric liquid monopropellant is ignitable via conventional detonation cords. Accordingly, in one example, electric liquid monopropellant can be packaged as discrete devices, e.g., ELP devices 100, and ignited via detonation cords within a well. ELP devices 100 can include plastic containers, bags, tubes, cylinders, hoses, and the like to package and contain electric liquid monopropellant as discrete propellant charges.

FIGS. 2A-2E illustrate various examples of wrapping or bringing a detonation cord 112 in proximity to an ELP device 100 to initiate combustion thereof. Generally, increasing the surface area of the ELP device 100 covered by the detonation cord 112 results in a faster, more uniform combustion of the liquid monopropellant within ELP device 100. Additionally, various wrap geometry and surface contact area configurations can be used to vary the combustion event's pulse shape as desired.

FIGS. 3A-3B illustrate examples where the liquid monopropellant within the ELP device 300 is ignited directly by heat or electricity (as opposed to being disposed adjacent or proximate a detonation cord external to the ELP device 300, i.e., where the electric liquid monopropellant is separated from the detonation cord by the packaging or container). For instance, in FIG. 3A, a detonation cord 312 may be passed through ELP device 300 directly, and thus in direct contact with electric liquid monopropellant 301 therein. In other examples, multiple detonation cords or a single cord spiraling within ELP device 300 may be used to increase the surface area of the detonation cord with respect to the liquid monopropellant therein.

FIG. 3B illustrates an example where electrically conductive wires 314 are within ELP device 320 or otherwise in electrical contact with liquid monopropellant 301 therein. Providing sufficient power to the conductive wires 314 ignites the liquid monopropellant 301. Conductive wires 314 may provide direct current, alternating current, or pulsed power to initiate combustion. In this example, liquid monopropellant within ELP device 300 would burn from left to right, however, multiple sets of conductive wires disposed within ELP device 300 are possible, including pairs disposed on opposing sides of ELP device 300, to provide other burn patterns and/or rates. Additionally, coils or plates could be used to spread the electric power to the liquid monopropellant 301.

FIG. 3C illustrates an exemplary design where an electric match 316, e.g., a resistive coil, spark, pyrotechnic device, or other device, is used to create sufficient heat within liquid monopropellant 301 of ELP device 300 to initiate ignition thereof. Similarly, ELP device 300 in this example would ignite and burn left to right, but multiple electric matches may be used in various configurations as desired.

FIGS. 4A-4C illustrate an exemplary method of using electric liquid monopropellant 401 within a well to create new cracks or fractures in surrounding structures. Beginning with FIG. 4A, a well tool 410 is inserted into a perforated well. An electric liquid monopropellant 401 is then pumped into the well casing and the surrounding perforated well as shown in FIG. 4B. The well may also be capped off or otherwise obstructed to increase the pressures within the perforated well, increasing the amount of electric liquid monopropellant into surround perforations. The electric liquid monopropellant 401 is then ignited to create new cracks or fractures 490 within the well. This process may be repeated if desired to further create new cracks or fractures within the well.

Further, in some examples, a down hole power source may be used for igniting propellant. In one example, one or more capacitors can be used and slowly charged over time and rapidly discharged to ignite the propellant.

Further, in some examples, low density ceramic proppants can be suspended within the electric liquid propellant and transported/dispersed into the newly formed rock fractures during the combustion event. Further, ignition of the electric liquid monopropellant can be initiated via a submerged container of catalyst that is thermally or mechanically breached to release the catalyst.

FIG. 5 illustrates an exemplary ELP device 500 that uses an elongated bag 540 containing electric liquid monopropellant 501 that can be disposed within a carrier gun 510. A detonation cord 512 can be run through or otherwise approximate the elongated bag 540 for detonation. The carrier gun 510 can then be disposed down well for detonation therein.

FIG. 6 illustrates an exemplary ELP device 600 that includes a container (e.g., a rigid plastic container or bag) 602, with a partially insulated electrode 660 passing through the liquid monopropellant 601. In this example, there is no detonation cord, and the electric liquid monopropellant will ignite at exposed portions of the electrode as described above with respect to FIG. 3B. The insulated electrode 660 can have selective areas 662 exposed along its length to provide a desired ignition pattern to the liquid monopropellant 601.

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated.

Although the disclosure and examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the claims. 

What is claimed is:
 1. An apparatus for fracturing wells, comprising: an electric liquid monopropellant device including a volume of electric liquid monopropellant, and a detonation cord in proximity to the electric liquid monopropellant device to ignite the volume of electric liquid monopropellant upon activation of the detonation cord.
 2. The apparatus of claim 1, wherein the detonation cord is adapted to ignite the electric liquid monopropellant at pressures exceeding 200 psi.
 3. The apparatus of claim 1, wherein the electric liquid monopropellant operable to combust at temperatures less than 300 degrees Celsius.
 4. The apparatus of claim 1, wherein the detonation cord is wrapped around the electric liquid monopropellant device.
 5. The apparatus of claim 1, further comprising a plurality of electric liquid monopropellant devices disposed within a well tool, and the plurality of electric liquid monopropellant devices in proximity to the detonation cord.
 6. The apparatus of claim 1, further comprising at least one shaped charge device, the at least one shaped charge device in proximity to the detonation cord to combust upon activation of the detonation cord.
 7. The apparatus of claim 6, wherein the at least one shaped charge device and the electric liquid monopropellant device are disposed within a well tool.
 8. The apparatus of claim 1, further comprising electrically conductive wires in contact with the electric liquid monopropellant for sensitizing the electric liquid monopropellant prior to combustion.
 9. An apparatus for fracturing wells, comprising: a container; and an electric liquid monopropellant within the container.
 10. The apparatus of claim 9, further comprising a detonation cord.
 11. The apparatus of claim 9, further comprising an electrode disposed within the electric liquid monopropellant for initiating combustion thereof.
 12. The apparatus of claim 11, wherein the electrode disposed within the electric liquid monopropellant is selectively exposed to ignite the liquid monopropellant.
 13. The apparatus of claim 9, further comprising an electric match disposed within the electric liquid monopropellant for initiating combustion thereof.
 14. A method for fracturing wells, the method comprising: introducing an electric liquid monopropellant into a well; and igniting the electric liquid monopropellant in the well, wherein the pressure exceeds 200 psi.
 15. The method of claim 14, wherein the electric liquid monopropellant is introduced via a well gun.
 16. The method of claim 14, wherein the electric liquid monopropellant further comprises ceramic proppants suspended therein.
 17. The method of claim 14, wherein the electric liquid monopropellant is further charged by a down hole power source. 